High-Precision Biochemical Sensing with Resonant Monocrystalline Plasmonic Ag Microcubes in the Mid-Infrared Spectrum

Area of Science:

• Plasmonics and Nanophotonics
• Spectroscopy
• Biochemical Sensing

Background:

• Infrared (IR) spectroscopic fingerprinting analyzes molecular composition via vibrational modes.
• Surface-enhanced mid-IR absorption spectroscopy (SEIRAS) offers sensitive molecular detection using plasmonic cavities.
• Current SEIRAS methods are limited by low-throughput nanofabrication, hindering scalability for biochemical sensing.

Purpose of the Study:

• To develop a scalable and efficient SEIRAS method for sensitive molecular detection.
• To overcome the limitations of current nanofabrication-based SEIRAS techniques.
• To enable broad biochemical sensing applications through improved IR spectroscopy.

Main Methods:

• Synthesized silver (Ag) cubic microparticles (Ag-CMPs) via a high-throughput wet-chemical process.
• Utilized on-resonance SEIRAS with Ag-CMPs dispersed on gold mirror substrates with an aluminum oxide spacer.
• Employed single-particle SEIRAS (SP-SEIRAS) for optical interrogation of individual Ag-CMPs.

Main Results:

• Demonstrated robust mid-IR plasmonic resonances in Ag-CMPs, supporting enhanced near-field light-matter interactions.
• Successfully detected polydimethylsiloxane (PDMS) and bovine serum albumin (BSA) monolayers by probing individual Ag-CMPs.
• Analyzed complex human peritoneal fluid (PF) samples using the SP-SEIRAS approach, overcoming bulk sample measurement challenges.

Conclusions:

• The developed Ag-CMP-based SP-SEIRAS method is scalable and efficient for IR spectroscopic fingerprinting.
• This technique significantly enhances sensitivity and specificity for molecular detection.
• The SP-SEIRAS method addresses key limitations, paving the way for widespread biochemical sensing applications.